Seat leakage is a major problem associated with severe service valves and one which can have a considerable cost to the user. Normally it is not possible to change a leaking valve or remedy the problem without shutting down the facility. This has a huge cost implication for such facilities as power stations, chemical plants and the like. It is, therefore, beneficial for users to be able to identify leaks and then monitor them over a period of time, thereby allowing necessary maintenance to be timetabled in with scheduled shutdowns. In addition, monitoring leaks enables a better understanding of efficiencies within the plant and how they can be improved.
Current methods for detecting leakage of valves have a number of problems associated with them. One method is to use infra-red imagery that comprises taking an image of the valve and adjacent pipework and visually looking at the varying temperatures. Leakage is manifested as a hot area extending downstream from the valve in the vicinity of the valve seat. This method enables leaks to be detected but requires the removal of the thermal insulation that usually surrounds the pipework and valve. In addition, while good for detecting leaks, it is not a reliable method for quantifying their size.
A second method is the use of ultrasonics. Again this is a good method of identifying a leak and works well in a laboratory situation, but in a noisy industrial environment, where sound is likely to be propagated along the pipes connected to the valves, it is not easy to obtain reliable enough results using this method.